1. Technical Field
The present invention relates to a method for acquiring a color value of a device-independent color space such as CIE XYZ using a scanner that outputs a color value of a device-dependent color space such as R, G, B.
2. Description of Related Arts
In recent years, there has been an increasing demand for color print in the field of production print. Further, highly precise color reproducibility is required of production print, and in most cases an enhanced color calibration is needed to meet the requirement. Meanwhile, it has been desired that the calibration be able to be conducted in a short time without the need for high-level knowledge.
As a method for conducting the calibration in a short time, it is conceivable to acquire a color value of a device-independent color space (standard color space) using a scanner equipped with a printer system such as disclosed in Patent Document 1 (Japanese Unexamined Patent Application Publication No. 2008-312117), for example.
In the Patent Document 1, for example, RGB data read by a scanner using a look-up table is converted to a color value of a device-independent color space, which is not dependent on the device. With regard to look-up table for converting from the read RGB, which is used for the conversion, to L*a*b*, an optimization is carried out based on the scanner device RGB data acquired by reading the profile creation chart and the colorimetric value (L*a*b*) of each color chart.
Further, in the Patent Document 1, it is attempted to solve, by adjusting the elements of the look-up table so as to decrease the chroma, such a problem (multi-to-one) that when color charts are read which are different in manuscript class such as printed manuscript and silver halide photography manuscript, the color charts are read as a plurality of different RGB data values at the scanner, due to scanner metamerism, even though the colorimetric values for the color chart read by the colorimeter are the same.
However, it is not necessarily possible to get a highly precise result of color measurement merely by optimizing the look-up table for converting from the read RGB to L*a*b*, based on the colorimetric values (L*a*b*) for the color charts, as disclosed in the Patent Document 1.
In particular, the Patent Document 1 does not recognize such a problem (one-to-multi) that when same-color patches in a color chart are formed of different K plate amounts, the patches are read as the same RGB data at the scanner while the colorimetric values from the colorimeter are not necessarily the same. Nor does the document refer to means for solving the problem.
The present invention has been made in view of the foregoing circumstances and has for an object to provide a scanner profile that makes it possible to achieve a highly accurate color conversion even if and when the scanner reads different colors as the same RGB data (one-to-multi).